Mark Bray is a historian of human rights, terrorism and political radicalism in Modern Europe who is currently a lecturer at Dartmouth College. He is the author of the forthcoming book, "Antifa: The Anti-Fascist Handbook."

Antifascists may seem like a novelty, but they’ve been around for a very long time. Maybe we should start listening to them. (Getty Images)

On Monday, President Trump capitulated to the popular demand that he distance himself from his comment that “many sides” were to blame in Charlottesville by explicitly denouncing white nationalism. “Racism is evil,” he appeared to grudgingly concede, “including the KKK, neo-Nazis and white supremacists.”

A day later, however, Trump reversed course by clarifying that there were “very fine people” at the white power rally, while casting “blame on both sides” including the allegedly “alt-left” antifa.

First bursting into the headlines when they shut down far-right provocateur Milo Yiannopoulos in February at the University of California at Berkeley, antifascists again captivated the public imagination by battling the fascists assembled at the “Unite the Right” white power rally in Charlottesville.

But what is antifa? Where did it come from? Militant anti-fascist or “antifa” (pronounced ANtifa) is a radical pan-leftist politics of social revolution applied to fighting the far right. Its adherents are predominantly communists, socialists and anarchists who reject turning to the police or the state to halt the advance of white supremacy. Instead they advocate popular opposition to fascism as we witnessed in Charlottesville.

There are antifa groups around the world, but antifa is not itself an interconnected organization, any more than an ideology like socialism or a tactic like the picket line is a specific group. Antifa are autonomous anti-racist groups that monitor and track the activities of local neo-Nazis. They expose them to their neighbors and employers, they conduct public education campaigns, they support migrants and refugees and they pressure venues to cancel white power events.

The vast majority of anti-fascist organizing is nonviolent. But their willingness to physically defend themselves and others from white supremacist violence and preemptively shut down fascist organizing efforts before they turn deadly distinguishes them from liberal anti-racists.

Antifascists argue that after the horrors of chattel slavery and the Holocaust, physical violence against white supremacists is both ethically justifiable and strategically effective. We should not, they argue, abstractly assess the ethical status of violence in the absence of the values and context behind it. Instead, they put forth an ethically consistent, historically informed argument for fighting Nazis before it’s too late. As Cornel West explained after surviving neo-Nazi attacks in Charlottesville, “If it hadn’t been for the antifascists protecting us from the neo-fascists, we would have been crushed like cockroaches.”

Though antifa are often treated as a new force in American politics since the rise of Trump, the anti-fascist tradition stretches back a century. The first antifascists fought Benito Mussolini’s Blackshirts in the Italian countryside, exchanged fire with Adolf Hitler’s Brownshirts in the taverns and alleyways of Munich and defended Madrid from Francisco Franco’s insurgent nationalist army. Beyond Europe, anti-fascism became a model of resistance for the Chinese against Japanese imperialism during World War II and resistance to Latin American dictatorships.

A World War II anti-fascism propaganda film found a new audience after the deadly white supremacist rally in Charlottesville, Va. on Saturday, Aug. 12. (The Washington Post)

Modern antifa politics can be traced to resistance to waves of xenophobia and the emergence of white power skinhead culture in Britain in the 1970s and ’80s. It also has its roots in self-defense groups organized by revolutionaries and migrants in Germany, as the fall of the Berlin Wall unleashed a violent neo-Nazi backlash.

In the United States and Canada, activists of the Anti-Racist Action Network (ARA) doggedly pursued Klansmen, neo-Nazis and other assorted white supremacists from the late 1980s into the 2000s. Their motto was simple but bold: “We go where they go.” If Nazi skinheads handed out leaflets at a punk show in Indiana about how “Hitler was right,” ARA was there to show them the door. If fascists plastered downtown Alberta’s Edmonton with racist posters, ARA tore them down and replaced them with anti-racist slogans.

Responding to small fascist groups may seem trivial to some, but the rise of Hitler and Mussolini show that resistance is not a light switch that can simply be flipped on in a crisis. Once the Nazi and fascist parties gained control of government, it was too late to pull the emergency brake.

In retrospect, antifascists have concluded, it would have been much easier to stop Mussolini back in 1919 when his first fascist nucleus had 100 men. Or to stamp out the far-right German Workers’ Party, which had only 54 members when Hitler attended his first meeting, before he transformed it into the National Socialist German Workers’ Party (the Nazi Party). Though the regimes that inspired their original protests are long dead, antifascists have devoted themselves to treating small fascist and Nazi groups as if they could be the nucleus of a murderous movement or regime of the future.

For years, antifascists have been maligned for treating groups of 40 or 60 Klansmen or fascists with the utmost seriousness. Members of the 10-year-old Rose City Antifa of Portland, Ore., the country’s oldest currently existing antifa group, confronted criticism even from the left for devoting themselves to unmasking and exposing the activities of small groups of local racists, Islamophobes and fascists rather than focusing on more large-scale, systemic injustices.

Years before the alt-right even had a name, antifascists were spending thankless hours scouring seedy message boards and researching clandestine neo-Nazi gatherings. They were tracking those who planted the seeds of the death that we all witnessed in Charlottesville. Agree or disagree with their methods, the antifa, who devote themselves to combating racism, are in no way equivalent to alt-right trolls who joke about gas chambers. Behind the masks, antifa are nurses, teachers, neighbors, and relatives of all races and genders who do not hesitate to put themselves on the line to shut down fascism by any means necessary.

It should not have taken the murder of Heather Heyer for so many of us, especially white people, to take seriously the threat of white power that has plagued communities of color for generations. The history of anti-fascist demands that we take seriously the violence of white supremacists. The days of “just ignoring them” are over.

Black bloc tactics are used by "antifascist action" or "antifa" protesters. Here's what that means. (Gillian Brockell/The Washington Post)